Adjustable Column Moulds: Sizes, Materials and Casting

Reading a mould size

Square adjustable moulds are listed with two figures — for example 425 × 600 mm — together with a forming height and a list of adjustable column sizes. The first figure describes the mould, the second the forming height of one set, and the adjustable list tells you the column widths the set can actually cast.

Round moulds are listed as height × diameter, for example 750 × 300 mm, meaning a 750 mm forming height in a 300 mm diameter. Since round moulds are not adjustable, each diameter is a separate mould.

How adjustment works

Adjustable square moulds carry a set of forming positions — a two-hole mould may cast 300 mm and 350 mm columns, while a five-hole mould casts 150 mm through 350 mm. The wider the adjustment range, the more of your size range a single set covers.

Adjustment is by fixed positions rather than continuous travel, so the column sizes you can produce are exactly the ones listed. If you need an intermediate size, check with your supplier whether an additional position can be tooled.

• Narrow range, small mould: better for one or two standard sizes at volume.
• Wide range, larger mould: better for yards producing a spread of sizes on demand.
• Adjustment positions are fixed — confirm the exact list before ordering.

PP, virgin PP or ABS

Column moulds are made from PP or ABS. Reprocessed PP is the standard option and the least expensive. Virgin PP gives a more consistent surface and better durability. ABS is the most rigid of the three and holds a sharper edge on the mould corners, which matters when the cast face is decorative and will be left as struck.

• Reprocessed PP — standard duty, most economical
• Virgin PP — better surface consistency and longer service life
• ABS — most rigid, sharpest edge detail on decorative faces

Casting and stripping

A mould is assembled around the casting position, filled and compacted, and stripped once the concrete has taken its initial set. Releasing the mould too early distorts the column; too late and the mould is difficult to remove and the surface can be torn.

Moulds should be cleaned and released between casts. A consistent release agent is what actually delivers the finish, and it also protects the mould surface from abrasion by the aggregate.

• Assemble the set square and check the forming position before pouring
• Compact in layers with a poker vibrator to avoid honeycombing
• Apply release agent every cast, not every few casts
• Clean and inspect the mould edges between casts